The present invention relates to a very low cost portable compact scanner. More particularly it is directed to a compact device employing a single scanning carriage having a reading head and a printing head securely comounted in the same plane to a planar mounting substrate.
Historically, copies of original documents have been produced by a xerographic process wherein the original document to be copied is placed on a transparent platen, either by hand or automatically through the use of a document handler, and the original document illuminated by a relatively high intensity light. Image rays reflected from the illuminated document are focused by a suitable optical system onto a previously charged photoconductor, the image light rays functioning to discharge the photoconductor in accordance with the image content of the original to produce an electrostatic latent image of the original on the photoconductor. The electrostatic latent image so produced is thereafter developed by a suitable developer material commonly referred to as toner, and the developed image transferred to a sheet of copy paper brought forward by a suitable feeder. The transferred image is thereafter fixed to the copy paper by fusing to provide a permanent copy while the photoconductor is cleaned of residual developer preparatory to recharging. More recently, interest has arisen in electronic imaging where, in contrast to the aforedescribed xerographic system, the image of the document original is converted to electrical signals or pixels and these signals, which may be processed, transmitted over long distances, and/or stored, are used to produce one or more copies. In such an electronic imaging system, rather than focusing the light image onto a photoreceptor for purposes of discharging a charged surface prior to xerographic development, the optical system focuses the image rays reflected from the document original onto the image reading array which serves to convert the image rays to electrical signals. These signals are used to create an image by some means such as operating a laser beam to discharge a xerographic photoreceptor, or by operating some direct marking system such as an ink jet, direct thermal or thermal transfer printing system.
It is generally advantageous if the normally separate document reading and copy printing operations could be combined. If some of these reading/writing functions could be combined, system operation and synchronization could be simplified and system cost reduced through the use of fewer parts.
There are systems in the prior art that address the above identified concerns. For example:
U.S. Pat. No. 4,496,984 to Stoffel and U.S. Pat. No. 4,583,126, a division of the above-identified reference, disclose an input/output scanner for simultaneously reading a document and writing a copy. The document and copy sheet are fed in back to back relation to the read/write station. A monolithic full width reading array reads each line in two steps, to improve resolution. The writing array consists of rows of ink jet nozzles, of which the number and disposition is in direct correspondence to the sensors of the read bar.
U.S. Pat. No. 4,424,524 to Daniele discloses a full width read/write LED array for scanning a document in the read mode or exposing the photoreceptor in the write mode. A Selfoc optical fiber lens array is used for focusing the full width LED array on the document and the frame assembly includes copy sheet and document or photoreceptor transport paths including means to index a document to the document path in a direction transverse to the first direction, and to index a copy sheet through the copy sheet path, in the opposite transverse direction of indexing said document.
U.S. Pat. No. 4,636,871 to Oi discloses a copying machine comprising separate reading and printing arrays and a scanning mechanism for moving the subject copy. A relative movement between the copying paper sheet and print element and between the document and read element is effected so that scanning is performed in the same pattern on both the reading and printing sides.
A difficulty with these prior art systems is the complexity and cost of separate components such as the complex optics, photoreceptor and developer in a typical xerographic process such as the Daniele system. In other systems such as the Stoffel system, it is necessary for an operator to manually combine a document and copy sheet into a single unit for manual insertion to the machine feed rolls. Such a system also has a significant cost penalty associated with components such as the monolithic full width reading array.
In the scanning carriage described in the above referenced copending application entitled Compact Multimode Input and Output Scanner, the input chip was mounted on a facet of the scanned print carriage which was remote from the surface on which the ink jet chip was mounted. While this is a workable arrangement, the control of the tolerances on the mounting of the input chip relative to the output chip and the mounting of both chips relative to the copy paper and the document is somewhat challenging in that each chip has very tight alignment tolerances in six dimensions, the X,Y,Z, axes and 3 rotational degrees of freedom, one about each axis. It is, for example, desired that the line of photo sights in the input chip be aligned in all six dimensions with the lines of sights on the ink jet chip to minimize pixel placement error. Any lack of true parallelism between the line of image receiving pixels on the input device and the image creating pixels on the print head device will result in image discontinuities or pixel placement errors between bands of images on the created copy. Accordingly, it is an object of the present invention to provide a scanner which minimizes these discontinuities.